US4835754A - Tracking control device of an optical pick-up - Google Patents

Tracking control device of an optical pick-up Download PDF

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Publication number
US4835754A
US4835754A US07/123,055 US12305587A US4835754A US 4835754 A US4835754 A US 4835754A US 12305587 A US12305587 A US 12305587A US 4835754 A US4835754 A US 4835754A
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United States
Prior art keywords
differential signal
frequency component
signal
compensating
pass filter
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Expired - Lifetime
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US07/123,055
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English (en)
Inventor
Kazutaka Yamamoto
Toshihiro Shigemori
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Ricoh Co Ltd
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Ricoh Co Ltd
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Assigned to RICOH COMPANY, LTD., A CORP. OF JAPAN reassignment RICOH COMPANY, LTD., A CORP. OF JAPAN ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: SHIGEMORI, TOSHIHIRO, YAMAMOTO, KAZUTAKA
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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
    • G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B7/0941—Methods and circuits for servo gain or phase compensation during operation
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
    • G11B7/085—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam into, or out of, its operative position or across tracks, otherwise than during the transducing operation, e.g. for adjustment or preliminary positioning or track change or selection
    • G11B7/08505—Methods for track change, selection or preliminary positioning by moving the head
    • G11B7/08517—Methods for track change, selection or preliminary positioning by moving the head with tracking pull-in only
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
    • G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B7/0901—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following only

Definitions

  • This invention generally relates to an optical pick-up for use in an optical disk apparatus, and, in particular, to a tracking control device of such an optical pick-up.
  • an optical disk as an optical recording medium
  • various information is recorded on a surface by forming pits of approximately 1 micron in diameter at a pitch of approximately 2 microns on a recording track of the surface using a laser beam light spot.
  • the recording track is defined in a pre-groove typically formed during manufacturing of an optical disk, and various information, such as identification information of a recording region and sync signal, necessary for proper management of recorded data is previously formed on the recording track. It is to be noted that such a recording track may be provided in plural number concentrically or singularly in a spiral format.
  • a laser beam is irradiated to the recording track of the optical disk and the light reflecting from the optical disk is picked up by an optical pick-up to thereby read the data recorded on the recording track.
  • a tracking control device typically includes a phase compensation circuit for compensating the gain of a tracking servo loop.
  • phase compensation circuit includes a delay phase compensation unit for compensating a control error (steady-state error) at a low frequency range and an advance compensation unit for securing stability of the tracking servo loop at intermediate and high frequency ranges.
  • a tracking control device suitable for use in an optical disk apparatus, which comprises a pair of photoelectric elements for receiving light reflecting from an optical disk, a differential amplifier connected to receive outputs from the pair of photoelectric elements to produce a differential signal, and a phase compensation circuit comprised of a phase advance compensation circuit 6 and a low pass filter as a phase delay compensation circuit, which are connected in parallel.
  • the outputs of the phase advance and delay compensation circuits are connected to an adder through first and second switches, respectively.
  • a comparator serving as a zero-cross detector is also provided for receiving the differential signal.
  • a pulse generator for supplying a bipolar drive pulse to the adder under the control of a controller which also controls the on/off state of each of the first and second switches.
  • a resultant output obtained from the adder is supplied to a driver for driving a moving coil of a tracking actuator.
  • the pulse generator In a normal tracking mode of operation, the pulse generator is held inoperative and the first and second switches are both turned on by the controller. On the other hand, in a track jump mode of operation, the pulse generator is rendered operative and the first switch is turned off while maintaining the second switch turned on by the controller.
  • a third switch is provided as connected to the input terminal of the low pass filter.
  • Another object of the present invention is to provide an improved tracking control device of an optical pick-up for use in an optical disc apparatus.
  • a further object of the present invention is to provide an improved tracking control device capable of controlling a normal tracking operation as well as a track jump operation.
  • a still further object of the present invention is to provide an improved tracking control device high in performance as well as in accuracy and stable and fast in operation.
  • FIG. 1 is an illustration showing how to combine FIGS. 1(a) and 1(b);
  • FIGS. 1(a) and 1(b), when combined as illustrated in FIG. 1, define a schematic illustration showing a tracking control device of an optical disc system constructed in accordance with one embodiment of the present invention
  • FIGS. 2(a) through 2(e) are waveforms which are useful for understanding the operation of the structure shown in FIGS. 1(a) and 1(b);
  • FIG. 3 is an illustration showing how to combine FIGS. 3(a) and 3(b);
  • FIGS. 3(a) and 3(b), when combined as illustrated in FIG. 3, define a schematic illustration showing a tracking control device of an optical disc system constructed in accordance with another embodiment of the present invention.
  • FIGS. 4(a) through 4(e) are waveforms which are useful for understanding the operation of the structure shown in FIGS. 3(a) and 3(b).
  • the tracking control system is typically incorporated in an optical pick-up and includes a photoelectric unit 1 for receiving light reflecting from an optical disk so as to detect an error in position of a light spot with respect to a recording track of the optical disk.
  • the photoelectric unit 1 is comprised of a pair of photoelectric elements so that it is provided with a pair of separate light-receiving surfaces for receiving the light reflecting from the optical disk.
  • the photoelectric unit 1 provides a pair of light current outputs which are supplied to respective current/voltage converting circuits 2 and 3, whereby the light current singals are converted into voltage signals. These two voltage signals are then supplied to a differential amplifier 4 which serves as a tracking error detecting circuit. As a result, a differential output from the differential amplifier 4 constitutes a tracking error signal A (see FIG. 4a). That is, since the amount of light of the light spot received by each of the pair of photoelectric elements of the photoelectric unit 2 differs from each other depending on the positional relationship between the light spot and a recording track of the optical disk, such a tracking error signal A can be obtained by processing these two light current outputs through the differential amplifier 4 after current-to-voltage conversion.
  • the phase compensation circuit includes a phase advance compensation circuit 6 and a low pass filter 7 serving as a phase delay compensation circuit, which are connected in series.
  • the output terminal of the phase advance compensation circuit 6 is connected to a first switch 8, and the output terminal of the low pass filter 7 is connected to a second switch 9.
  • the comparator 5 is defined as a zero cross detecting comparator for detecting the fact that the tracking error signal A output from the differential amplifier 4 crosses zero level, and the comparator 5 outputs an output signal B as shown in FIG. 4(b) to a controller 10.
  • a pulse generating circuit 11, or more specifically kick pulse generating circuit, is also connected to the controller 10.
  • the pulse generating circuit 11 provides a bipolar drive pulse D (see FIG. 4(d)), which is a drive signal in a track jump control mode for moving a light spot on the surface of an optical disk in the radial direction, typically from one recording track to another recording track adjacent thereto radially.
  • the reason why the drive pulse D is bipolar, i.e., having both of negative and positive components, is based on the fact that, in a track jump operation, acceleration is applied to the movement of a light spot by one of the positive and negative pulses and then deceleration is applied to the movement of the light spot by the other of the positive and negative pulses.
  • the selection of the order of positive and negative pulses depends on whether a light spot moves inwardly or outwardly.
  • an output from the phase advance compensation circuit 6, an output C from the low pass filter 7, and an output D from the pulse generating circuit 11 are all input to an adder 12 which outputs an added result as a drive signal E.
  • This drive signal E is then supplied to a moving coil 14 of a tracking actuator of the optical pick-up through a driver amplifier 13. As a result, the optical pick-up is moved relative to the associated optical disk radially in accordance with the drive signal E to bring the optical pick-up in alignment with a recording track of the optical disk.
  • the on/off status of each of the first and second switches 8 and 9 is controlled by the controller 10. And, in a normal tracking mode of operation, the pulse generating circuit 11 is held inoperative, so that no output D is produced. In addition, both of the first and second switches 8 and 9 are rendered on by the controller 10. Under the condition, the tracking actuator, including the moving coil 14, is controlled using an added value of outputs from the phase advance compensation circuit 6 and the low pass filter 7 as a control signal. In this instance, a signal output from the phase advance compensation circuit 6 contributes to provide a driving force against intermediate and high frequency track shift and also to maintain stability in the servo system.
  • the signal C output from the low pass filter 7 contributes to provide a driving force against a low frequency track shift due, for example, to external disturbances and eccentricity of the optical disk. Since both of the first and second switches 8 and 9 are normally closed, there is defined a tracking servo loop, so that the light spot on the optical disk can follow an information recording track of the optical disk properly.
  • the pulse generating circuit 11 is activated by the controller 10 so that the track jump drive pulse D is output from the pulse generating circuit 11.
  • the switch 8 is set open and the switch 9 is closed by the controller 10.
  • an acceleration pulse having a predetermined polarity e.g., positive polarity if the light spot is to be moved outwardly
  • a predetermined polarity e.g., positive polarity if the light spot is to be moved outwardly
  • the moving coil 14 of a tracking actuator for moving the optical pick-up with respect to the associated optical disk is driven by this acceleration pulse, so that the optical pick-up moves radially outwardly to an adjacent recording track. It is to be noted that it may be so constructed to move the entire optical pick-up or any part thereof, such as an objective lens of the optical pick-up.
  • the light spot moves on the optical disk radially outwardly to be located on the adjacent recording track. Accordingly, the light distribution on the two-part photoelectric unit 1 varies, so that the tracking error signal A changes from a maximum value of one polarity to another maximum value of the other polarity. And, the zero cross point during this change corresponds to the center of the recording track. At the timing of the occurrence of this zero cross point, the signal B is output from the comparator 5 and then supplied to the controller 10.
  • the controller 10 causes the pulse generating circuit 11 to switch the drive pulse D from the acceleration pulse to a deceleration pulse, which is opposite in polarity, e.g., negative polarity.
  • the tracking actuator including the moving coil 14, is decelerated to thereby cause the optical pick-up to be positioned above the adjacent recording track.
  • the first switch 8 is turned on or closed by the controller 10 to thereby define the normal tracking servo loop.
  • an optical disk it is typically driven with a radial misalignment due, for example, to an error in mounting to a drive shaft and eccentricity of the optical disk. For this reason, a recording track defined on the optical disk also has a radial misalignment in most cases. Such a radial misalignment causes a light spot to be shifted away from the recording track when the optical disk rotates; however, such a radial misalignment can be absorbed by providing a tracking servo loop which keeps a light spot to be properly positioned with respect to a recording track.
  • the drive signal output from the adder 12 would have a shape as shown in FIG. 4(d), which does not include error correction components (i.e., components for compensating for the radial misalignment of a recording track) in the drive signal as different from the drive signal shown in FIG. 4(e).
  • error correction components i.e., components for compensating for the radial misalignment of a recording track
  • the radial misalignment of a recording track can be properly compensated for or absorbed to thereby allow to position the light spot in alignment with the adjacent recording track after track jump. That is, in accordance with the present embodiment, during the track jump mode, the first switch 8 is turned off or set open and the second switch 9 is turned on or closed by the controller 10. Under this condition, during the track jump mode, the drive signal from the pulse generating circuit 11 is added with the output C from the low pass filter 7 by the adder 12 and the resulting drive signal E is applied to the moving coil 14 of the tracking actuator.
  • the information regarding the radial misalignment of a recording track which is a low frequency component of the differential signal A, is included in the drive signal E as shown in FIG. 4(e), so that the radial misalignment of a recording track can be suitably corrected, thereby allowing to carry out a track jump operation securely.
  • a second embodiment of the present invention is directed to correct such a track error signal to further improve the track jump operation.
  • FIGS. 1(a) and 1(b) illustrate a tracking control system constructed in accordance with another embodiment of the present invention. It is to be noted that the embodiment shown in FIGS. 1(a) and 1(b) is structurally similar in many respects to the embodiment shown in FIGS. 3(a) and 3(b), so that like elements are indicated by like numerals.
  • the present embodiment shown in FIGS. 1(a) and 1(b) differs in structure from the previous embodiment shown in FIGS. 3(a) and 3(b) in that a third switch 15 is additionally provided between the differential amplifier 4 and the low pass filter 7. The on/off status of the third switch 15 is controlled by the controller 10, and the third switch 15 is normally kept on or closed. During the track jump mode, the third switch 15 is turned off or set open by the controller 10.
  • the first and third switches 8 and 15 are kept off and the second switch 9 is kept on. That is, outputting from the phase advance compensation circuit 6 is inhibited, and while the input side of the low pass filter 7 set open or disconnected, the output C of the low pass filter 7 and the drive pulse D output from the pulse generating circuit 11 are added at the adder 12, and the resulting drive signal E is applied to the moving coil 14 of the tracking actuator as a feedback control signal. As a result, a leakage signal from the low pass filter 7 at the time of crossing a recording track is eliminated.
  • the low pass filter 7 is capable of holding the voltage immediately prior to the track jump, compensation for the radial misalingnment of a recording track, which constitutes the low frequency component of the differential signal A, can be carried out.
  • the low pass filter 7 is also used as a holding circuit for holding the voltage immediately prior to track jump to provide compensation for the low frequency component of the differential signal A.
  • the voltage held by the low pass filter 7 decreases in accordance with a time constant of the low pass filter 7; however, since the track jump processing time period is extremely short and an error in the holding voltage is extremely small, the voltage held by the low pass filter 7 may be considered to be sufficiently smooth and substantially at constant during a track jump operation, as shown in FIG. 2(c).

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  • Moving Of The Head For Recording And Reproducing By Optical Means (AREA)
  • Optical Recording Or Reproduction (AREA)
  • Moving Of Head For Track Selection And Changing (AREA)
  • Moving Of The Head To Find And Align With The Track (AREA)
US07/123,055 1986-11-21 1987-11-19 Tracking control device of an optical pick-up Expired - Lifetime US4835754A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP61-278271 1986-11-21
JP61278271A JPS63131332A (ja) 1986-11-21 1986-11-21 光ピツクアツプのトラツキング制御装置

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US07/123,055 Expired - Lifetime US4835754A (en) 1986-11-21 1987-11-19 Tracking control device of an optical pick-up

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US (1) US4835754A (enrdf_load_stackoverflow)
JP (1) JPS63131332A (enrdf_load_stackoverflow)
DE (1) DE3739631A1 (enrdf_load_stackoverflow)

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4896310A (en) * 1987-07-31 1990-01-23 Sony Corporation Light beam control arrangements for optical disc apparatus
US4899325A (en) * 1987-05-07 1990-02-06 Fujitsu Limited Fine access method and circuit for an optical disk drive using a multi-track jump
US4975895A (en) * 1987-08-28 1990-12-04 Fujitsu Limited Track servo control system for optical disk apparatus
US5054013A (en) * 1989-03-13 1991-10-01 Pioneer Electronic Corporation Track transverse detection signal generating circuit
US5164646A (en) * 1990-07-20 1992-11-17 Pioneer Electronic Corporation Tracking servo system
WO1996000461A1 (en) * 1994-06-24 1996-01-04 Quantum Corporation Actuator retraction circuit
US5629914A (en) * 1995-03-20 1997-05-13 International Business Machines Corporation Data-transition threshold following in optical recording
US5757747A (en) * 1996-01-16 1998-05-26 Kabushiki Kaisha Toshiba Tracking servo signal processing circuit and read apparatus using the same
US6222802B1 (en) * 1997-05-19 2001-04-24 Samsung Electronics Co., Ltd. Device and method for automatically controlling sled loop gain in optical disc drive
US20030058753A1 (en) * 2001-09-03 2003-03-27 Samsung Electronics Co., Ltd. Apparatus and method of removing disturbances
US20040125730A1 (en) * 2002-12-27 2004-07-01 Kazutaka Yamamoto Optical disk recording apparatus that records a visible image on an optical disk
US20050122869A1 (en) * 2001-09-12 2005-06-09 Kazutaka Yamamoto Information recording scheme for preventing recording failure resulting from impact or vibration

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0778892B2 (ja) * 1988-12-05 1995-08-23 松下電器産業株式会社 トラッキングサーボ方法およびトラッキングサーボ装置
KR20030085345A (ko) * 2002-04-30 2003-11-05 주식회사 에이엠티 광디스크 드라이브의 포커스 및 트랙킹 서보 시스템

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4544838A (en) * 1981-10-30 1985-10-01 Olympus Optical Co., Ltd. Method and apparatus for detecting tracking error
US4613963A (en) * 1982-06-25 1986-09-23 Pioneer Electronic Corporation Tracking-servo device
US4677602A (en) * 1983-04-05 1987-06-30 Pioneer Electronic Corporation Device for controlling recording track jump operations with over-run correction
US4698795A (en) * 1984-06-13 1987-10-06 Pioneer Electronic Corporation Tracking servo device

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4443869A (en) * 1981-09-28 1984-04-17 Rca Corporation Track jump servo system for disc player
JPS58166567A (ja) * 1982-03-26 1983-10-01 Matsushita Electric Ind Co Ltd 情報トラックの検索装置

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4544838A (en) * 1981-10-30 1985-10-01 Olympus Optical Co., Ltd. Method and apparatus for detecting tracking error
US4613963A (en) * 1982-06-25 1986-09-23 Pioneer Electronic Corporation Tracking-servo device
US4677602A (en) * 1983-04-05 1987-06-30 Pioneer Electronic Corporation Device for controlling recording track jump operations with over-run correction
US4698795A (en) * 1984-06-13 1987-10-06 Pioneer Electronic Corporation Tracking servo device

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4899325A (en) * 1987-05-07 1990-02-06 Fujitsu Limited Fine access method and circuit for an optical disk drive using a multi-track jump
US4896310A (en) * 1987-07-31 1990-01-23 Sony Corporation Light beam control arrangements for optical disc apparatus
US4975895A (en) * 1987-08-28 1990-12-04 Fujitsu Limited Track servo control system for optical disk apparatus
US5054013A (en) * 1989-03-13 1991-10-01 Pioneer Electronic Corporation Track transverse detection signal generating circuit
US5164646A (en) * 1990-07-20 1992-11-17 Pioneer Electronic Corporation Tracking servo system
WO1996000461A1 (en) * 1994-06-24 1996-01-04 Quantum Corporation Actuator retraction circuit
US5495156A (en) * 1994-06-24 1996-02-27 Quantum Corporation Actuator retraction circuit
US5629914A (en) * 1995-03-20 1997-05-13 International Business Machines Corporation Data-transition threshold following in optical recording
US5757747A (en) * 1996-01-16 1998-05-26 Kabushiki Kaisha Toshiba Tracking servo signal processing circuit and read apparatus using the same
US6222802B1 (en) * 1997-05-19 2001-04-24 Samsung Electronics Co., Ltd. Device and method for automatically controlling sled loop gain in optical disc drive
US20030058753A1 (en) * 2001-09-03 2003-03-27 Samsung Electronics Co., Ltd. Apparatus and method of removing disturbances
US7116607B2 (en) * 2001-09-03 2006-10-03 Samsung Electronics Co., Ltd. Apparatus and method of removing disturbances during optical recording and/or reproducing
US20050122869A1 (en) * 2001-09-12 2005-06-09 Kazutaka Yamamoto Information recording scheme for preventing recording failure resulting from impact or vibration
US6975573B2 (en) 2001-09-12 2005-12-13 Ricoh Company, Ltd. Information recording scheme for preventing recording failure resulting from impact of vibration
US7196990B2 (en) 2001-09-12 2007-03-27 Ricoh Company, Ltd. Information recording scheme for preventing recording failure resulting from impact or vibration
US20040125730A1 (en) * 2002-12-27 2004-07-01 Kazutaka Yamamoto Optical disk recording apparatus that records a visible image on an optical disk
US7215625B2 (en) 2002-12-27 2007-05-08 Ricoh Company, Ltd. Optical disk recording apparatus that records a visible image on an optical disk

Also Published As

Publication number Publication date
JPS63131332A (ja) 1988-06-03
DE3739631A1 (de) 1988-06-01
DE3739631C2 (enrdf_load_stackoverflow) 1989-06-08

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